The present invention relates to coupling systems for mounting tubes obliquely onto surfaces where the surface and the tube may be undergoing relative vibration, and particularly, to coupling systems for mounting tubes to components of a vehicle motor.
A modern motor vehicle requires or is provided with a variety of accessory apparatus which involve the use of tubes to transmit pressurized fluid (such as exhaust) or to provide a vacuum, to a portion of the motor block, carburetor, intake or exhaust manifolds, or other component. For example, an EGR (Exhaust Gas Recirculation) tube directs hot exhaust gases from the exhaust manifold or other part of the exhaust system, to the carburetor or air intake manifold, which improves fuel efficiency, and as well, improves the quality of the vehicle exhaust emissions.
Typically, the tube will be insertingly received at one end directly into an aperture provided in the sidewall of a motor component. The end of the tube may be provided with an outwardly extending, annular bead, to, in part, limit the extent to which the tube extends into the sidewall of the motor component, and as well to provide a surface a clamp member to bear on, to hold the tube end in place. In addition, the bead serves to create a seal between the wall of the engine component and the clamp member, which is typically a simple plate-like retainer member with a bolt extending through one end of the plate-like member into the wall of the motor component. The annular bead is typically simply formed as a corrugation mechanically formed into the end of the tube. When the clamp member is tightened down against the wall of the motor component, the bead, being fabricated from relatively thin and flexible metal material, axially compresses, slightly to form a tight sealing fit between the tube, the aperture and the wall and clamp member.
A typical prior art tube, such as may be used to draw off exhaust gases from an exhaust manifold in a automotive engine, will have an outside diameter to wall thickness ratio of 39:1 to over 62:1. For example, a tube having a wall thickness of 0.012 inches may be formed with an outside diameter of 0.625 inches. In such a tube material, an outwardly projecting annular bead can be formed which may have a radius of, for example, 0.10 inches, extend radially outwardly from the outer diameter of the tube a distance of about 0.11 inches, and have a thickness (measured along the direction of the tube) of about 0.25 inches. The use of such thin-walled tubular material is not practical in some environments. For example, in the environment of a larger engine, thus requiring longer developed tube length, or in an environment where substantially robust duty life is required, with external damage potential, such thin-walled tubes may not be durable enough, or economically practical. Accordingly, it is desirable to employ a tube having a much lower ratio of the outside diameter to the wall thickness. Such a more robust tube may have a ratio of outside diameter to wall thickness of between 17:1 and 20:1. For example, an outside diameter of 0.6 inches would be accompanied by a tube wall thickness of 0,035 inches.
An effective seal at the point of connection of such a thick-walled tube to an engine component housing is difficult to obtain, for the reason that the relatively thicker-wailed tube does not permit the forming of a desirable annular bead having overall dimensions and spring rate similar to those in an annular bead which can be readily formed in a thin-walled tube. The thicker material, when formed into a bead shape, will not deflect elastically under required clamp pressure, leading to undesirable leakage, possible damage or hazard, and inefficiency.
Accordingly, it is desirable to provide a thicker-walled tube for use in such situations as an EGR tube, for use in heavier duty environments, but which is capable of being sealingly connected to the appropriate component housing in as effective a manner as can be achieved with thin-walled tubes.
One possible solution to this problem, is to affix beyond the end of a thick-walled tube a short extension adapter section of thin-walled tube into which an appropriate annular bead has been formed. The two components are slightly overlapped and welded or brazed. While the adapter extension formed of the thin-walled tube enables an effective sealing connection to be provided, the composite tube which has been formed would prove unsatisfactory in that the thin-walled adapter extension is susceptible to the vibration and other thermal or mechanical forces exerted upon it by the mass of the thick-walled tube. The greater, substantial mass of the remaining length of the heavier tube exerts potentially destructive force on the thin-walled adapter extension, as the tube length grows thermally and moves under the vibrations of the operating engine.
Accordingly, it is desirable to provide a coupling system for connecting a relatively thick-walled tube to a wall, for example, of a motor component, which has the benefit of the features of a thin-walled tube coupling.
A further object of the invention is to provide a coupling system which has a composite construction utilizing a thin-walled tube adapter portion which is operably connected to a tube end of a thick-walled tube.
Still another object of the invention is to provide such a coupling system which is more able to withstand the vibration and stresses associated with continued operation, with enhanced durability of the seal formed between the bead and the aperture, and improve the connection joint strength between the thin-walled tube adapter portion and the thick-walled tube end.
These and other objects of the invention will become apparent in light of the present specification, claims and drawings.